In a typical communications setting involving a master device and one or more slave devices (i.e., master-slave communications), the slave device's responses to data request messages are of a fixed length. The response therefore may contain irrelevant data that causes unnecessary bus traffic, thus slowing down data throughput in the system.
It is desirable to use a variable length response message, which allows the slave device to respond with only the necessary, meaningful data required to provide an appropriate response to the master device, eliminating unnecessary bus traffic and improving data throughput capacity.